Means of adjusting air speed in different areas of a paint spray booth have been devised in the past. According to U.S. Pat. No. 5,173,118 (Josefsson, filed May 20, 1991), air speed is controlled by ten perforated plates slidable laterally with respect to each other such that the size of perforations is adjusted.
According to U.S. Pat. No. 4,537,120 (Josefsson, filed Apr. 20, 1983), separate zones of a paint spray booth can have different air velocities circulating in them.